A substrate treating apparatus and a substrate transporting method. A platform is placed on a first ID block, and a platform is placed on a second ID block. A currently-used carrier platform is provided only on the first ID block. A substrate is transported in both a forward path and a return path between the first ID block and an IF block. The substrate is sent in the return path from the IF block to the second ID block disposed between a coating block and a developing block without being transported from the IF block to the first ID block. Consequently, transportation process in the return path by the coating block disposed between the first ID block and the second ID block is reduced. As a result, an entire throughput of a substrate treating apparatus can be enhanced.